Cervical cancer is a leading form of cancer among women. In the United States alone, there are believed to be more than two million cases of precancerous cervical abnormalities annually. The U.S. also sees, on average, about sixty five thousand cases of cervical carcinoma and about sixteen thousand cases of invasive cervical cancer. Although screening is less common outside the Unites States, nearly half a million cases of cervical cancer are detected each year around the world.
Cervical cancer frequently begins as a precancerous lesion of the cervix. These lesions are also known as cervical intraepithelial neoplasia. If left untreated, these lesions can deepen over time and ultimately develop into an invasive cancer of the cervix and associated tissues. Fortunately, early detection followed by appropriate treatment results in a very high cure rate for cervical cancer.
Therefore, it is quite important that at least certain factions of the female population undergo regular screening. These factions include patients with previous cervical abnormalities and those who have a family history of cervical abnormalities. Women who are sexually active are at greater risk and should undergo regular screening, as are those who test positive for HPV (human papillomavirus). This is a sexually transmitted virus that in some forms can cause genital warts.
During the 1940""s, Dr. George Papanicolaou developed a screening test which bears his name and which has become the most widely used screening technique for detecting abnormal cervical cells. Today, this test is known more commonly as the PAP test or the PAP smear test. Typically, the PAP test is performed in the physician""s office as part of a woman""s routine gynecological examination. The test involves collecting cervical cells via a brush, stick or swab that is used to loosen and then collect cells that can be examined microscopically.
Cervical samples taken for the purposes of Pap testing are deposited on a planar microscope slide, fixed to prevent cell loss or degradation, and stained in a manner that accentuates and differentiates the various cellular structures. These prepared samples are subjected to detailed microscopic evaluation by a cytotechnologist or pathologist to detect and classify any cellular abnormalities that may be present in the cells deposited on the microscope slide. The results of these evaluations are reported to the attending physician who determines whether additional evaluation or treatment of the patient is required.
The Pap test as it is currently practiced is time consuming and requires a highly skilled supporting infrastructure. Even in countries with the necessary infrastructure, several weeks can elapse between taking the sample and reporting the results of the evaluation to the attending physician. The uncertainty attendant in this delay is stressful to the patient. As it is not practical or the patient to be retained at the medical facility until the results of the evaluation have been returned, it is necessary for the attending physician to contact the patient to inform them that the results of the test were negative or, conversely, if the results were positive, to arrange for a follow-up visit.
In the US, fewer than 60% of the patients contacted with positive results actually present themselves for follow-up evaluations or treatment. This percentage is lower in other countries and is particularly low in public health screening programs and clinics that deal predominantly with transient populations and populations that are remote from the site of testing. Furthermore, depending upon the particular patient population, between 50 and 90 percent of all Pap samples taken are determined to contain no evidence of cellular abnormalities. This high percentage of negative samples imposes a substantial burden on the health care system and diverts resources from making cervical screening tests more widely available.
It is therefore desirable to provide a means of cervical screening that can produce a determination of whether a sample does or does not contain evidence of cellular abnormalities within the time frame of a typical cervical examination. As such a means provides the test results before the patient leaves the examination area, the uncertainty and stress of waiting for a negative diagnosis is eliminated and patients showing positive results can be retained for immediate follow-up and treatment.
Identifying those patients showing no signs of cellular abnormalities at the time of the initial examination also reduces the number of samples that must be sent to a laboratory for evaluation. This reduces the non-productive burden on the health care system and frees resources that can be used to increase the availability of cervical screening and other diagnostic testing.
The manner in which a positive result is followed up varies substantially by country. In some countries such as the U.S., a finding of ASCUS (atypical squamous cells of undetermined significance) or higher is generally considered to be grounds for follow-up or medical intervention. In other countries, the standard of care is to follow up or intervene in cases where the detected degree of abnormality corresponds to LSIL (low-grade squamous intraepithelial lesions) or HSIL (high-grade squamous intraepithelial lesions) and higher, but, in recognition that many lower grade abnormalities are benign or revert to normal over time, to ignore lower grade detected abnormalities. It is therefore desirable to be able to establish a reporting threshold that is consistent with the prevailing standard of care.
Cervical abnormalities generally present in the form of lesions or localized clusters of abnormal cells. The sampling methods utilized in current cervical screening procedures acquire cells from these lesions, but then disperse these cells into a typically much larger number of normal cells obtained from outside of the boundaries of the lesion. This dispersion results in the evaluation of a conventional cervical sample being an exercise in the detection of a rare event, that is, finding one or a few abnormal cells within a background consisting of a very large number (50,000-300,000) of normal cells. Dispersion also precludes using the sample to determine the location of the lesion on the cervix.
It is therefore desirable that a means of sampling and evaluation be provided that retains the spatial relationships that exist between the cells in-vivo. Retaining these relationships effectively eliminates dispersion and allows mapping of the test results onto the cervix for the purpose of guiding follow-up or intervention.
Accordingly, the invention is found in a system whereby cervical cells can be accurately and sufficiently obtained from a patient and can subsequently be quickly screened to determine if further analysis is warranted. The invention is found in a system in which cervical cells can be sampled in a way that maintains the spatial orientation in which the cells are located prior to sampling.
Therefore, the invention is directed to a cell analysis system that includes a collector for collecting a spatially arranged cell sample from a target tissue, and an analyzer that examines the cell sample for abnormal cells while the cell sample remains on a surface of the collector.
Other features and advantages of the present invention will be apparent from the following detailed description and drawings.